1. Field of the Invention
This invention relates to an improved process for the production of water-soluble soybean extract. More particularly, this invention relates to a water-soluble soybean extract having a relatively high protein content and superior organoleptic characteristics which is obtained by a process that is relatively simple and efficient.
2. Description of the Background
A basic concept in soybean extraction processes is to recover protein from soybeans in concentrated form. Although other uses for soybean protein concentrates have been disclosed in the prior art, protein concentrates in general are well known for their use as a beverage, e.g., such as a milk substitute or as a component of high protein food products.
A threshold or common denominator of many processes for concentrating soybean protein has been the extraction of these proteins using a variety of solvents. In this regard, many processes disclosed in the prior art have involved organic solvents such as pentane, hexane and/or various alcohols requiring complicated and costly processing equipment and materials.
Similarly, a number of extraction processes known in the prior art utilize water as the soybean protein solvent. However, significant disadvantages are also associated with such processes. For example, such processes have heretofore not overcome significant problems with aroma, flavor and bitterness of the soybean product. In this regard, it is known to produce a soybean extract by the steps of soaking the soybeans followed by milling, extraction in an aqueous phase, separation of the resultant slurry and heating the soluble product. Processes of this kind, however, typically result in a soybean extract having what many consider to be an offensive aroma and taste.
It is also known in the art that the objectionable organoleptic characteristics of soybean extracts can be reduced by crushing the soybeans in the presence of water maintained at an elevated temperature. In this regard, it is believed that the unpleasant taste and aroma associated by many with the soybean concentrates of the prior art are due to the presence of volatile compounds having a relatively low molecular weight. These compounds are produced during the disintegration of the soybean grain with water by the action of the enzyme lipoxidase on unsaturated fatty acid chains. Approximately 80 of these compounds have, thus far, been isolated and roughly half have been identified, the majority of these having unpleasant odors. For example, ethyl-vinylketone, is one of these compounds, the addition of only 5 ppm of which to a water-soluble soybean extract is sufficient for the detection of the characteristic unpleasant taste and aroma of soybeans.
As mentioned previously, the heating of water-soluble soybean extract after the disintegration does not avoid the offensive organoleptic characteristics of the extract. Conversely, heating a soybean product prior to disintegration avoids the unpleasant taste and flavor but results in a relatively low yield of soluble protein concentrate.
The problems suggested in the preceding paragraphs are not intended to be exhaustive, but rather are among many which detract from the effectiveness of prior art processes for producing a water-soluble soybean extract. Other noteworthy problems may also exist. However, those presented hereinabove should suffice to demonstrate that processes for producing soluble soybean extracts appearing in the prior art have no been altogether satisfactory.
Hence, a need still continues to exist for water-soluble soybean extracts devoid of the detrimental characteristics which plague the prior art extracts and a method of preparing thereof.